Simulate a split washer getting tightened down
The method I'm using is very easy to animate; however you have to model the washer using the screw modifier.
This is the mesh for my washer. It is just those selected edges on the right in the image below. Notice the placement of the mesh relative to the object origin (it's the orange dot in the red box).

It is the screw modifier that actually generates the whole washer (it is displayed in wireframe in the image above.)
The most important setting is the Screw, think of that as the offset. The bigger that number the farther apart the beginning will be from the end. Set it to whatever makes your washer look correct, mine is ¼ of an inch.

Now to animate this thing
It is the &quot;Screw&quot; value that gets animated to squash the washer.
To set a keyframe, hover over the Screw value in the modifier and press I. Or you could RMB  on the Screw value then choose Insert Keyframe.
Now move ahead in the timeline, set the Screw value to 0 (the washer will be flat) and insert another keyframe, same as the first one.